These days, various types of communication controllers are proposed in order to control communication of movable communication terminal devices such as mobile telephones and the like. In such a communication controller, a communication system of global standard such as W-CDMA (Wide band Code Division Multiple Access) or UMTS (Universal Mobile Telecommunications System) is applied. According to the above communication system, a single frequency bandwidth is shared by multiple users by multiplexing codes, whereby the frequency efficiency is excellent and high-speed communication is made available in a flexible manner by selecting the code. The conventional technique for the above communication system is described in Non-Patent Document 1.
A general W-CDMA system will now be described with reference to FIG. 8. In the system as shown, UE (User Equipment) 1 is managed by a base transceiver station NodeB 02. The NodeB 02 is controlled by an RNC (Radio Network controller) 02. The RNC 02 is managed by an MSC/SGSN (Mobile Switching Center/Serving GPRS Support Node) 5.
The MSC/SGSN 5 also manages an RNC 01 as well as the RNC 02. A node controlled by the RNC 01 is indicated by Node 01.
The unit of a radio network including the RNC and the NodeB under the RNC is referred to as RNS (Radio Network Subsystem). In the drawing, the RNC 01 and the RNC 02 are shown and included in an RNS 01 and an RNS 02, respectively. In addition, the network including the MSC/SGSN 5 is referred to as a CN (core Network) 8. Furthermore, the whole system on the radio network side is referred to as UTRAN (UMTS terrestrial radio access network).
Meanwhile, Uu represents the interface between the UE 1 and the UTRAN, lur represents the interface between the RNC 01 and the RNC 02, and lu represents the interface between the UTRAN and the CN.
In a UTRAN, when the UE 1 moves while maintaining communication, an RNC 3 that controls calling of the UE 1 is fixed as an S-RNC (Serving-RNC), allowing the S-RNC to remotely control an RNC, namely D-RNC (Drift-RNC) that manages a cell where the UE 1 exists (also represented as existing in a cell, which denotes existing in a communication area). Such a technique is herein referred to as subscriber line extension method.
An RNC, to which a connection request is given at the start of communication, serves as an S-RNC. The S-RNC is not changed by the movement of the UE 1, as long as the subscriber line extension method is continuously employed. However, the S-RNC may be changed in the middle of communication by an S-RNC Relocation.
Non-Patent Document 1: 3GPP Technical Standard TS 21.101
Non-Patent Document 2: 3GPP Technical Report TR 25.933